1. Field of Endeavor
The present invention relates to the field of rotating electrical machines.
2. Brief Description of the Related Art
EP-A1-0 166 114 and EP-A2-0 633 643 disclose horizontal-axis electrical machines in which a built-in stator is mounted in a housing which can be split horizontally, by means of a plurality of supporting rings (supporting plates) which are arranged one behind the other in the axial direction and are at a distance from one another. The supporting rings are connected to the housing lower part via attachment parts at opposite points on their external circumference, and are otherwise surrounded by the housing, at a distance. The built-in stator has compression beams, which run distributed in the axial direction, on its outer circumference. In the area of the compression beams, the built-in stator is braced in the supporting rings by means of attachment wedges. This type of installation is mainly used to transmit the thermally dependent axial and radial expansions of the laminated stator core as uniformly as possible to the housing.
The basic configuration of a known machine such as this can be seen in FIG. 6a. The electrical machine 10′ has an approximately cylindrical built-in stator 11, which concentrically surrounds the machine axis and a rotor that is not illustrated. The built-in stator 11 is surrounded on the outside by a housing 12, which is composed of a housing upper part 13 and a housing lower part 14. The housing lower part 14 and the housing upper part 13 are detachably connected to one another by means of a separating flange 15 on a horizontal plane. The built-in stator 11 is firmly wedged to the compression beams 17 by means of wedges in a plurality of supporting rings 29, only one of which can be seen in FIG. 6a. The supporting rings 29 are connected to the housing lower part 14 via an attachment apparatus 28 at two horizontal opposite points, and are at a distance from the housing 12 over the rest of their circumference. The built-in stator 11 is located freely in the housing between the supporting rings 29, as is illustrated in FIG. 2.
However, the described way of installation leads to a number of problems. On the one hand, undesirable deformation of the housing 12 can occur when the machine is raised by means of ropes on bollards (16 in FIG. 2) during transportation, with these bollards themselves being fitted to the outside of the housing 12, for this purpose; on the other hand, the housing can start to oscillate during operation of the machine, not only causing noise but also mechanically loading the entire structure.
In the past, solutions as shown in FIGS. 1 and 6 have been implemented for both problems. As shown in FIG. 1, the housing deformation during lifting of the machine was reduced by providing locking apparatuses 18′ between the housing, or the housing lower part 14, and the built-in stator 11. The individual locking apparatus 18′ includes a threaded sleeve 19, which is mounted directly underneath the separating flange 15 on the housing lower part 14 and points radially inwards, and into which a locking screw 20 is screwed from the inside. For locking, the locking screw 20 is unscrewed, with the housing upper part removed, to such an extent out of the threaded sleeve 19 that the upper face of the screw head 21 is pressed against the compression beam 17 that is fitted to the built-in stator 11. When the locking screw 20 reaches its limit position, it is fixed in the threaded sleeve 19 by a fixing screw 22. Once all of the locking screws have been positioned appropriately on the built-in stator, the housing is closed. The lock between the housing and the built-in stator 11 prevents housing deformation during lifting on the bollards by means of a wire cable during transportation. However, the lock remains positioned on the built-in stator 11 in the installation, during operation. This influences the vibration behavior of the housing during operation and can lead to undesirable high local or global oscillation amplitudes.
As shown in FIG. 6, coupling pieces 30 are used in order to reduce housing oscillations during operation, and provide a firm coupling between the housing 12 and the built-in stator suspension (supporting ring 29). This fixed coupling directly via that part of the separating flange 15 which is associated with the housing lower part 14 leads, however, at least in some cases to high local or global oscillation amplitudes. Furthermore, the coupling to the housing lower part 14 can result in a non-uniform oscillation behavior in comparison to the housing upper part 13 which, in extreme cases, can lead to fracture of the screw 31 on the separating plane between the housing lower part 14 and the housing upper part 13 (separating flange 15).